Method of producing metal beams with a top-hat profile

ABSTRACT

A method for producing metal beams having a top-hat profile comprises the hot rolling of slabs (13), ingots (12), billets, preliminary profiles (14) or similar semifinished products in a rolling train. The rolling train comprises at least two roll stands. Using at least two shaping passes during a single rolling process in a number of rolling stations at hot-rolling temperature, preferably simple irregular pass design turns an entering cross section (10) of a one-part semifinished product into an exiting cross section having a top-hat profile (A), which corresponds geometrically more or less to the profile of the finished product.

TECHNICAL FIELD

The disclosure relates to a method of producing metal beams having atop-hat profile by hot rolling a metal primary material.

BACKGROUND

A method of producing metal beams having a top-hat profile is generallyknown, for example from CN 102431568 A. This method relates to theproduction of a center longitudinal beam by hot rolling a three-partarrangement of different semifinished products. The top-hat profile isassembled from two U-shaped profiles and an upper cover plate to form adownward-opening U-shape, wherein the individual parts are produced byhot rolling.

Producing center longitudinal beams from two hot-rolled Z-profileswelded together to form a top-hat profile is also known. This isfollowed by the usual finishing steps such as straightening, annealing,etc. This method is relatively complex in terms of the work stepsrequired. Welding the Z-profiles results in a microstructural change inthe heat-affected zone of the Z-profile. This results in inhomogeneityin the microstructure and material composition. Different materialcompositions in the region of the weld seam can lead to corrosion. Inaddition, testing of the finished weld seam, for example by means ofultrasound, is required. In addition, a weld seam also has geometricdisadvantages. For example, a notch effect is created by the weld seam.In addition, the material may warp during welding. The weld seam causesstability problems at the beginning and end of the seam. By joiningseveral parts, the errors are added up, such that higher errortolerances ultimately result. Finally, material differences of differentZ-profiles from different batches are also problematic.

WO 2007/008152 A1 describes a method for cold rolling a top-hat profilein a single work operation in a rolling device provided for thispurpose. The rolling device for producing the desired profile is knownfrom EP1 339 508 B1. With the method, the top-hat profile is rolled oredged, as the case may be, from a flat sheet as primary material. Thismethod is only suitable for processing relatively thin sheets as primarymaterial.

SUMMARY

The invention is based on the object of providing a simplified methodfor the production of top-hat profiles that avoids the disadvantagesdescribed above.

The object is achieved by a method as claimed.

A method is proposed for producing metal beams having a top-hat profileby hot rolling a one-piece semifinished product. In particular, a methodfor the production of metal beams having a top-hat profile, compriseshot rolling of slabs, ingots, billets or similar semifinished productsin a rolling train. The rolling train comprises at least two rollstands. Using at least two shaping passes during a single rollingprocess in a number of rolling stations at hot-rolling temperature,preferably with simple irregular roll pass design, turns an enteringcross section of a one-part semifinished product into an exiting crosssection having a top-hat profile, which substantially correspondsgeometrically to the profile of the finished product. Within the meaningof the present disclosure, “substantially” means that the exiting crosssection of the hot-rolled section corresponds to the geometry anddimensions of the finished product except for minor angular deviationsof the individual legs of the profile.

The method is carried out without any further intermediate steps by hotrolling relatively thick semifinished products as primary materials upto the substantially finished product in a hot-rolling train. Thereby,forming a one-piece semifinished product uses at least two shapingpasses during a single rolling process in a plurality of rollingstations at hot-rolling temperature. The exiting cross section of thetop-hat profile is preferably generated with simple irregular passdesign by shaping rolls or shaping passes/precise shaping rolls, as thecase may be. Precise shaping is understood to mean profile rolling forproducing a profile of a defined finished cross section from a definedinitial cross section with a defined number of rolling passes, wherein asimple irregular pass design is understood to mean a precise shapingwith which the distribution of the height change over the profile widthhas at least one plane of symmetry.

Hot-rolling temperature refers to a temperature of the rolled materialthat is above the recrystallization temperature of the material. In thecase of steel as the primary material, this is a temperature well above900° C. Forming at hot-rolling temperature also means that the rolledmaterial or the semifinished products, as the case may be, are only athot-rolling temperature or have been heated to hot-rolling temperaturebefore the first pass or before the first forming pass. The otherforming passes can be carried out at a correspondingly lower rollingtemperature.

Optionally, the rolled material can be heated before and/or after theindividual rolling steps or passes, as the case may be, for example byusing heating devices in the form of induction furnaces or the like.

Preferably, the temperature when carrying out the first forming pass orat the first roll stand, as the case may be, is between 950° C. and1300° C.

Examples of semifinished products are slabs with a rectangular crosssection and dimensions of 500 mm to 1200 mm×150 mm to 450 mm, so-called“blooms” with dimensions of 400 mm to 700 mm×150 mm to 450 mm orso-called “beam blanks” (pre-profiles). The latter can, for example,have a width of 400 mm to 750 mm and a height of 400 mm to 500 mm.

It is advantageous if the entering cross section of the semifinishedproduct has a rectangular cross section whose material distributioncorresponds approximately to the material distribution to be producedwith a first pass of the rolling process.

The hot rolling process can be carried out with a wide variety of standconfigurations and rolling methods. In the case of rolling in pure duomode (using duo roll stands), for example, provision can be made to formthe entering cross section of the semifinished product to the exitingcross section using seven to thirteen shaping passes.

According to a variant of the method, the rolling process is carried outwith an open arrangement of at least two, preferably from three toeight, roll stands arranged side by side. Such an open rolling train isdescribed, for example, in DE 39 02 889 C2.

Alternatively, the rolling process is carried out using four to eightroll stands arranged one behind the other.

Thereby, the rolling operation can be carried out using roughing rollstands and finishing stands in tandem arrangement, in a manner that isat least partially reversing. A tandem arrangement is generallyunderstood to mean several roll stands moved together, through which therolled material passes one or more times. With this configuration, thefinishing roll stands can be operated in reversing mode.

Alternatively, the rolling process can be carried out using four to tenroll stands arranged one behind the other, comprising roughing rollstands, finishing roll stands in tandem arrangement operated inreversing mode, and finishing roll stands operated in continuous mode.

In another variant of the method, the rolling process can be carried outusing seven to eighteen roll stands using roughing roll stands and/orroll stands in tandem arrangement, which are operated in reversing mode,and finishing roll stands, which are operated continuously.

Finally, the rolling process can be carried out completely continuouslyusing seven to twenty roll stands arranged one behind the other, forexample in a continuous rolling train.

In principle, the rolling process can be carried out using duo rollstands and/or universal roll stands. A universal roll stand isunderstood to mean a roll stand with four rolls per stand, wherein twoof the rolls are arranged horizontally and two rolls are arrangedvertically.

Preferably, a geometric measurement of the rolled material is carriedout prior to and/or after each rolling station or forming pass, as thecase may be. Such a measurement can be performed by laser and caninteract with a hydraulic adjustment of the rolls of the individual rollstands.

After the last rolling pass or forming pass, as the case may be, acooling treatment of the top-hat profile produced or the rolledmaterial, as the case may be, for microstructure adjustment can beprovided, preferably using a simulation model and/or a microstructuredetector. Microstructure detection can be performed by means of laser orultrasound.

With a preferred variant of the method, it is provided that, after thelast forming pass of the rolling operation, the inclination of theflanges of the top-hat profile is between 0.1 and 15 degrees relative toa perpendicular to the axis of symmetry of the top-hat profile.

It is expedient that the rolling process is followed by a bendingprocess, preferably with a straightening machine or a bending device.The bending process transforms the profile into its final shape, inwhich the legs and crossbars of the top-hat profile are substantiallyperpendicular to each other.

The bending operation can be carried out by means of a bending deviceafter the last roll stand of the hot-rolling train or with an additionaluniversal roll stand.

The rolling process can be operated in “batch or semi-endless mode (hotcharging).”

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained below with reference to a forming processillustrated in the drawing. The drawing shows alternative semifinishedproducts and profiles after successive forming passes.

DETAILED DESCRIPTION

The entering cross section of the semifinished product to be hot-rolledis designated by reference numeral 10. This entry cross section 10 isrectangular and has a material distribution that roughly corresponds tothe material distribution of the first forming pass. The semifinishedproduct to be formed is, for example, a block 11 (bloom) withrectangular dimensions between 400 mm and 700 mm×150 to 450 mm, which isformed into the top-hat profile designated with reference character Ausing ten successive forming passes. The successive forming passes ofthe calibration for producing the top-hat profile are designated withreference numerals 1 to 10. Reference characters H to A therebydesignate the successively generated profiles. For this purpose, in theexemplary embodiment described, ten shaping passes are required, whichpasses can be carried out, for example, in ten duo roll stands arrangedone behind the other. As can be readily seen from the finished top-hatprofile A after the forming pass 10, it still exhibits slight angulardeviations from a strictly rectangular geometry. The finished top-hatprofile A is, for example, the top-hat profile of a center longitudinalbeam. The angular deviations after the last forming pass 10 areeliminated by a bending operation, for example by means of astraightening machine or by means of an additional universal roll standafter the last forming pass. In the illustrated exemplary embodiment,the inclination of the flanges 12 of the top-hat profile A relative to ahorizontal line is approximately between 0.1 and 15 degrees.

Alternatively, the primary material for the forming process or thesemifinished product to be formed, as the case may be, can be the slab13 also shown in the drawing with rectangular dimensions between 500 mmand 1200 mm×150 mm to 450 mm or the preliminary profile 14 withdimensions between 400 mm and 750 mm×400 mm to 500 mm.

LIST OF REFERENCE SIGNS

1-10 Forming passes

H to A Profiles

11 Entering cross section

12 Block (bloom)

13 Slab

14 Preliminary profile (beam blank)

1.-13. (canceled)
 14. A method for producing metal beams having atop-hat profile (A), comprising: hot rolling semifinished products in arolling train with at least two roll stands, wherein an exiting crosssection having a top-hat profile is formed from an entering crosssection of a one-part semifinished product using at least two shapingpasses during a single rolling process in a plurality of rollingstations at hot-rolling temperature, and wherein the exiting crosssection substantially corresponds geometrically to a profile of afinished product.
 15. The method as in claim 14, wherein thesemifinished products are slabs (13), ingots (12), billets, orpreliminary profiles (14).
 16. The method as in claim 14, wherein the atleast two shaping passes have a simple irregular pass design.
 17. Themethod according to claim 14, wherein the entering cross section of theone-part semifinished product has a rectangular cross section whosematerial distribution corresponds approximately to a materialdistribution to be produced with a first pass of the hot rolling. 18.The method according to claim 14, wherein the entering cross section ofthe one-part semifinished product is formed into the exiting crosssection using seven to thirteen shaping passes.
 19. The method accordingto claim 18, wherein the hot rolling is at least partly carried out withduo roll stands.
 20. The method according to claim 14, wherein the hotrolling is carried out with an open arrangement of three to eight rollstands arranged side by side.
 21. The method according to claim 20,wherein the hot rolling is carried out using four to eight roll standsarranged one behind the other.
 22. The method according to claim 21,wherein the hot rolling is carried out using roughing roll stands andfinishing roll stands in tandem arrangement, in a manner that is atleast partially reversing.
 23. The method according to claim 14, whereinthe hot rolling is carried out using four to ten roll stands arrangedone behind the other, comprising roughing roll stands, finishing rollstands in tandem arrangement operated in reversing mode, and finishingroll stands operated in continuous mode.
 24. The method according toclaim 14, wherein the hot rolling is carried out using seven to eighteenroll stands using roughing roll stands and/or roll stands in tandemarrangement, which are operated in reversing mode, and finishing rollstands, which are operated continuously.
 25. The method according toclaim 14, wherein the hot rolling is carried out completely continuouslyusing seven to twenty roll stands arranged one behind the other.
 26. Themethod according to claim 14, wherein the hot rolling is carried outusing duo roll stands and/or universal roll stands.
 27. The methodaccording to claim 14, wherein, after a last forming pass (10) of thehot rolling, an inclination of flanges of the top-hat profile (A) isbetween 0.1 and 15 degrees relative to a perpendicular to an axis ofsymmetry of the top-hat profile.
 28. The method according to claim 14,wherein the hot rolling is followed by a bending process with astraightening machine or a bending device.